#include <cstdio>

long long int fib[100];

int main()  {
  int i, n;
  
  fib[1] = fib[2] = 1;
  for (i = 3; i <= 90; i++) {
    fib[i] = fib[i - 2] + fib[i - 1];
  }
  
  while (scanf("%d", &n) == 1) {
    printf("%lld\n", fib[n]);
  }
  
  return 0;
}
